Adhesive performance of a multi-mode adhesive system: 1-Year in vitro study

Objectives The aim of this study was to investigate the adhesive stability over time of a multi-mode one-step adhesive applied using different bonding techniques on human coronal dentine. The hypotheses tested were that microtensile bond strength (μTBS), interfacial nanoleakage expression and matrix metalloproteinases (MMPs) activation are not affected by the adhesive application mode (following the use of self-etch technique or with the etch-and-rinse technique on dry or wet dentine) or by ageing for 24 h, 6 months and 1 year in artificial saliva. Methods Human molars were cut to expose middle/deep dentine and assigned to one of the following bonding systems (N = 15): (1) Scotchbond Universal (3M ESPE) self-etch mode, (2) Scotchbond Universal etch-and-rinse technique on wet dentine, (3) Scotchbond Universal etch-and-rinse technique on dry dentine, and (4) Prime&Bond NT (Dentsply De Trey) etch-and-rinse technique on wet dentine (control). Specimens were processed for μTBS test in accordance with the non-trimming technique and stressed to failure after 24 h, 6 months or 1 year. Additional specimens were processed and examined to assay interfacial nanoleakage and MMP expression. Results At baseline, no differences between groups were found. After 1 year of storage, Scotchbond Universal applied in the self-etch mode and Prime&Bond NT showed higher μTBS compared to the other groups. The lowest nanoleakage expression was found for Scotchbond Universal applied in the self-etch mode, both at baseline and after storage. MMPs activation was found after application of each tested adhesive. Conclusions The results of this study support the use of the self-etch approach for bonding the tested multi-mode adhesive system to dentine due to improved stability over time. Clinical significance Improved bonding effectiveness of the tested universal adhesive system on dentine may be obtained if the adhesive is applied with the self-etch approach.